He grunted a lot, admittedly. He war-whooped. He hollered, “Great song!” and “You go, girl,” and he probably was the noisiest guy in the spin class.

Now a Manhattan hedge-fund manager is paying dearly for his vociferous workout – the victim, his lawyer says, of a vicious spine-crushing “spin rage” attack by an angry classmate who’d heard enough.

“My concussion is healing,” victim Stuart Sugarman, 48, said yesterday from his hospital bed. “But I’ve had extensive back surgery – they actually used cadaver discs to repair the six discs in my neck.”

Meanwhile, Christopher Carter – the 44-year-old Manhattan broker accused of furiously hurling both Sugarman and his Schwinn stationary bike into the wall of an Upper East Side Equinox – remains free on misdemeanor assault charges.

“He snapped,” said the victim’s lawyer, Samuel Davis. “Spin class is an environment where there is passion in their pedaling – but there shouldn’t be violence.”

Ten days ago, Sugarman was sitting on his exercise bike at the Equinox on East 85th Street. The spin instructor was exhorting, the music was blasting, and Sugarman was shouting and rigorously pedaling away.

“My client was in what’s called ‘the zone,’ ” said Davis.

Davis described the sequence of events this way:

First, the furious broker demanded the hedge-fund manager please stop making so much noise. “Then it escalates to ‘Shut up!’ and “Shut the f— up!”

The broker complained to the instructor, who “basically shrugs,” Davis said.

The broker then allegedly issued the final ultimatum – “If you don’t shut the f— up, I’m getting off my bike.” The hedge-fund manager said: “Stop being a baby.”

Finally, the ballistic broker dismounts and “charges my client’s bike like Leonard Marshall of the New York Giants hitting a practice sled,” Davis said.

The broker tipped the hedge-fund manager and his bike into the wall, smashing a hole in the sheetrock, Davis said. “Then he smashes him back onto the ground, with the bike falling on top of him.”

Sugarman still has no feeling in his left side. He may need more surgery.

Carter’s lawyer, Dan Ollen, called Sugarman “a piece of work.”

“The first thing he does after the incident is hop on his bike and work out another 40 minutes,” he said. “The second thing he does is hire a personal-injury lawyer and the third thing he does is alert the media.

“Who’s kidding who?”

An Equinox spokesman said, “This is now a police matter and we are supporting their investigation.”